Annotate a screenshot, free, in your browser

Annotating a screenshot is the fastest way to make a visual point: an arrow at the broken button beats a paragraph describing where the broken button is. This page covers doing it in a browser tab, free, with no extension and no signup. The rest of the solutions hub covers the specific tools this replaces.

How to annotate a screenshot (step by step)

To annotate a screenshot or image: open CobaltCapture in your browser, add the image, drag arrows, boxes, or circles onto it, then export or share — no install, no signup. The full steps:

1. Open cobaltcapture.com in any browser tab. Nothing to install, no account needed to start.
2. Add your image. Capture the screen directly, paste a screenshot from the clipboard, or drag an image file in. PNG and JPEG both work.
3. Draw your markup. Click Annotate, then drag on the image: arrows, boxes, and circles are drag-to-draw; text labels are click-to-place; numbered pins drop in order. Hold Shift to keep a box or circle square.
4. Adjust anything. Drag a mark's outline to move it, click its ✕ to delete it, and double-click a text label to edit the words (one tap on a phone). Deleting a numbered pin renumbers the rest automatically.
5. Export or share. Download the marked-up PNG, export markdown / PDF / Word, or copy the public link. The markup is burned into the image, so it survives wherever you send it.

That's the whole task. The sections below cover what you can draw, how the native Mac and Windows tools handle it, how the top annotation tools compare, and where an annotated screenshot is the entire deliverable.

How to annotate a screenshot on Mac

To annotate a screenshot on a Mac, use the built-in Markup tools: after taking a screenshot, click its floating thumbnail to open Markup, or open any image in Preview and click the Markup toolbar button. Both give you arrows, shapes, text, and a signature tool, free and already installed. The three native routes:

• Screenshot app (Cmd+Shift+5). Press Cmd+Shift+5 for the capture toolbar, Cmd+Shift+4 to grab a region, or Cmd+Shift+3 for the full screen. After the shot, a thumbnail floats in the bottom-right corner for a few seconds. Click it to open Markup, then use the shape, arrow, text, and highlight tools in the top toolbar.
• Preview Markup. Double-click an existing image to open it in Preview, then click the Markup button (the pen-tip-in-a-circle icon) in the toolbar. You get sketch, shapes, arrows, text boxes, a signature tool, and colour and stroke controls. Saving writes the markup back into the file.
• Quick Look. Select an image file in Finder and press Space to preview it, then click the Markup icon at the top-right of the Quick Look window to annotate without opening any app.

macOS has no native way to drop numbered pins or export markdown, and the markup is only kept once you save. For a numbered-pin review you can share as a link or hand to a coding agent, that is where a browser tool like CobaltCapture picks up.

How to annotate a screenshot on Windows

To annotate a screenshot on Windows, press Win+Shift+S to capture a region with the Snipping Tool, click the notification that appears, and use the pen, highlighter, shapes, and text tools to mark it up. The Snipping Tool is built into Windows 10 and 11 and needs no install. The steps:

1. Press Win+Shift+S. The screen dims and a small toolbar lets you drag a rectangle, freeform, window, or full-screen selection.
2. The capture copies to the clipboard and a notification appears in the bottom-right. Click it to open the snip in the Snipping Tool editor.
3. Use the pen and highlighter to draw freehand, the shapes tool for rectangles and arrows, and the text tool to add labels. Shapes and text arrived in the Windows 11 Snipping Tool updates; older builds have pen and highlighter only.
4. Save as PNG or JPG, or paste the marked-up image straight into a ticket or chat.

For more shape options you can paste the capture into Paint and use its line, shape, and text tools. Neither built-in tool exports markdown or produces a shareable review link, which is the gap a browser tool fills when the annotated shot has to reach a developer or an AI coding agent.

What you can put on the image

Four shapes and a pin, which is the set that does almost all the work in practice:

• Arrows. Drag from the tail to the head. Point at the thing.
• Boxes and circles. Drag from corner to corner. Hold Shift to constrain to a square or a circle.
• Text labels. Click to place, type, press Enter. Single line, three sizes, positioned as a fraction of the image width so they scale with it.
• Numbered pins. Drop a marker and it takes the next number automatically. Delete one and the rest renumber themselves.

Everything comes in a seven-colour palette chosen to stay visible on real interfaces: red, orange, yellow, green, pink, black, white. Text labels get a contrasting halo drawn behind them, so light text stays legible on a light screenshot and dark text on a dark one, which is the failure mode most annotation tools leave you to solve by hand.

Drag a shape's outline to move it. Click its ✕ to delete it. Double-click a label to edit the words (on a phone, one tap).

The part that matters: the markup is in the file

Plenty of tools show you annotations in their own viewer and then hand you a bare screenshot the moment you export. CobaltCapture composes the marks into the PNG itself, on the server. The arrow you drew is in the pixels.

That means the marked-up image is what shows up in the markdown export, the PDF, the Word document, and the public share link, and it stays correct when someone drags the image into Slack or a ticket. It also means an AI coding agent reading the review sees the same arrow you drew, not a description of it.

Annotating a website, honestly

If you searched for a way to annotate a website, be clear on which of two things you want.

Some tools install a browser extension that pins comments onto the live page, so the markup is attached to the DOM and moves as the site changes. That's a real category, and if you need it, Markup.io and Pastel are built for it.

CobaltCapture works on a capture of the site: you grab the screen, mark up the still, and share it. You lose the live-DOM attachment. You gain that there is nothing to install, nothing to sign up for, and whoever opens your link needs neither — which is usually what decides whether a client actually replies.

Getting the marked-up image where it needs to go

The annotated image doesn't stay in CobaltCapture. Export it as a markdown document, a PDF, or a Word file, or copy the public review link and hand it over directly. The markdown pastes cleanly into a GitHub or GitLab issue, a Linear or Jira ticket, or a Slack message, with the marked-up image already embedded, not a separate attachment to keep track of.

If the reader is a coding agent instead of a person, there's a version with no export step at all. Connect the Cobalt MCP server to Claude Code, Cursor, or another MCP-aware agent, and it can call get_review on the URL to receive your notes as text plus the annotated screenshot as a real image, the arrow and the pin included, not a description of them.

That's the difference from a screenshot tool bundled inside a bigger project-management suite: no Jira seat, no workspace login, no app to install, just a browser tab and a link anyone, or any agent, can open.

Where a screenshot annotation is the whole deliverable

• Design review. Circle the spacing that's wrong, arrow the wrong font weight, send the link. See design review for the full workflow.
• Bug reports. A box around the broken state and a pin numbered 1: that your written repro steps refer to.
• Client feedback. Mark up the build, add the question you want answered next to each mark.
• Quick how-tos. Numbered pins are a step list that lives on the image instead of underneath it.

Best screenshot annotation tools compared

The best screenshot annotation tool depends on the job: CobaltCapture for no-install, in-browser markup you can share as a link or hand to an AI coding agent; Snagit or CleanShot X for a full desktop annotation suite with video; Greenshot or ShareX for a free power-user tool on Windows, if you are on Windows; Markup.io for pinning comments on a live website. How the common tools compare:

Tool	Price	Install / browser	Annotation types	Export formats	Best for
CobaltCapture	Free	Browser, no install	Arrows, boxes, circles, text, numbered pins	PNG, markdown, PDF, Word, public link	No-install markup you can share as a link or hand to an AI coding agent
Snagit	Paid (one-time license, ~$40+)	Desktop app (Win/Mac)	Full suite: arrows, callouts, shapes, step tool, blur, stamps	PNG, JPG, PDF, MP4, GIF	Power users who need a deep annotation suite plus video
CleanShot X	Paid (~$29 one-time on Mac; subscription for cloud)	Desktop app (Mac)	Arrows, shapes, text, highlight, blur, step counter	PNG, JPG, MP4, GIF, cloud links	Polished Mac captures and short screen recordings
Greenshot	Free (Windows; paid on Mac)	Desktop app	Arrows, boxes, highlight, text, obfuscate	PNG, JPG, BMP, PDF, clipboard	A free, lightweight annotator on Windows
Markup.io	Paid (~$79/mo, 14-day trial, no free tier)	Browser (+ extension for live sites)	Pinned comments on live sites, images, PDFs, video	Shareable links, integrations	Pinning feedback on a live website for client approval
ShareX	Free (open source)	Desktop app (Windows)	Arrows, shapes, text, step, blur, highlight	Many image formats plus upload destinations	A free power-user capture tool with automation

Competitor pricing and features change often; verify the current details on each vendor's site (checked August 2026).

There is no single winner. If you are marking up a screenshot on your own Mac or Windows machine just for yourself, the built-in tools in the sections above are enough. If you need a full annotation suite with a shape library, OCR, and video, Snagit or CleanShot X is the better call. If you want the free option and you are not on Windows, note that the free Greenshot and ShareX builds are Windows-only, and that Lightshot still wants a download. CobaltCapture is the right pick when the annotated screenshot has to reach someone else fast, with no install on either end, or be read directly by a coding agent.

What it does not do

Worth saying plainly, because the wrong tool wastes your afternoon:

• No multi-line or wrapped text callouts. Labels are one line each.
• No blur or redaction tool. If you need to hide a customer's data before sharing, crop it out.
• No scrolling or full-page capture. You annotate the frame you captured, not a stitched full-page image.
• No live-DOM pinning, as above.

If you need a full annotation suite with a shape library and OCR, Snagit and CleanShot X are genuinely better at that job, and both pages say so. This is the right tool when the annotated screenshot needs to reach someone else, fast, without either of you installing anything.

Frequently asked questions

How do I annotate a screenshot without installing anything?

Open CobaltCapture in a browser tab, add your screenshot (capture the screen, paste from the clipboard, drag the file in, or pick it with Add image), then choose Annotate and drag on the image to draw. Arrows, boxes, and circles are drag-to-draw; text labels are click-to-place. Nothing is installed and no account is needed to start.

Is there a free screenshot annotation tool?

This one. Capture, annotation, export, and public sharing are all free with no trial countdown and no per-seat plan. Most desktop annotation tools charge a one-time license or a subscription; the browser-based ones usually want a Chrome extension first.

Can I annotate a JPEG or only PNGs?

Both. Paste or drag in any common image, PNG or JPEG (WebP works too), or capture the screen directly. Whatever you start with, the export is a PNG with your markup burned into the pixels, so the marked-up image renders anywhere you send it.

Can I edit or undo an annotation after placing it?

Yes. Drag any mark's outline to reposition it, click its ✕ to remove it, and double-click a text label (one tap on a phone) to change the words. Delete a numbered pin and the remaining pins renumber themselves automatically, so the order in your notes stays correct.

What can I draw on the screenshot?

Arrows, rectangles, ellipses, and single-line text labels, each in a seven-colour palette, plus numbered pins for referencing a spot in your written notes. Hold Shift while dragging to constrain a box or circle to a perfect square or circle. Up to 24 marks per image.

Does the markup stay on the image when I share or download it?

Yes. The annotations are drawn into the PNG on the server, not layered over it in the browser, so the marked-up image is what appears in the markdown, PDF, and Word exports and what anyone sees at the share link. Nothing is lost when the file leaves the tool.

Can I annotate a website?

You annotate a capture of the website rather than the live page itself. Capture the screen (or paste a screenshot), mark it up, and share it. There is no browser extension pinning comments onto a live DOM, which is the tradeoff for needing no install and no signup from whoever opens the link.

Can I annotate a screenshot on my phone?

Yes. Take a screenshot the normal way, open the site, and use Add image, then draw with your finger. Tap a text label to edit it. Screen capture itself is desktop-only because mobile browsers have no API for it, but everything after that works on touch.

Do I need a Jira or project-management account to mark up and share a screenshot?

No. CobaltCapture is a standalone browser tab, not a feature bundled inside a bigger PM suite. Mark up the image, then export markdown, PDF, or Word, or copy the public review link, and paste it into whatever tracker you actually use. A coding agent can also read the annotated screenshot directly over MCP, no export step at all.